Rigid rods polymers

Figure 4.9 X-ray structure of [Ag(dmb)2]TCNQ - 1.5TCNQ° - The parallel Ag(dmb)j polymer chains are seen along their z-axis where the Ag zig-zag are clearly seen. The TCNQ ") bi-dimen-sional network lies between the polymer rigid rods. The box indicate the unit cells...

S. H. R. Askari, D. Soonil, F. Wudl, Substituted poly(phenylene vinylene) conducting polymers rigid-rod polymers with flexible side chains, Polymeric Materials Science and Engineering 1988, 59, 1068. 

PBO fiber was commercialized by Toyobo Co. in 1998 after about 20 years research in United States and Japan with the trade name Zylon. Poly benzo [l,2-d 5, 4-rf ]bisoxazole-2,6-diyl-l,4-phenylene (PBO) (Scheme 9.5) belongs to the class of high performance fibers commonly known as rigid-rod polymers. Rigid rod polymers are classified into lyotropic and thermotropic liquid crystalline polymers. Lyotropic and thermotropic polymers show liquid crystallinity in... 

Many complex systems have been spread on liquid interfaces for a variety of reasons. We begin this chapter with a discussion of the behavior of synthetic polymers at the liquid-air interface. Most of these systems are linear macromolecules however, rigid-rod polymers and more complex structures are of interest for potential optoelectronic applications. Biological macromolecules are spread at the liquid-vapor interface to fabricate sensors and other biomedical devices. In addition, the study of proteins at the air-water interface yields important information on enzymatic recognition, and membrane protein behavior. We touch on other biological systems, namely, phospholipids and cholesterol monolayers. These systems are so widely and routinely studied these days that they were also mentioned in some detail in Chapter IV. The closely related matter of bilayers and vesicles is also briefly addressed. 

Finally, rigid-rod polymers can be deposited on a solid substrate by the LB teclmique. These materials have both... 

Cased W, Sauer T and Wegner G 1988 Soluble phthalocyaninato-polysiloxanes—rigid rod polymers of high molecular-weight/Macromo/. Chem. Rapid Commun. 9 651-7... 

The principal classes of high performance fibers are derived from rigid-rod polymers, gel spun fibers, modified carbon fibers, synthetic vitreous fibers, and poly(phenyiene sulfide) fibers. 

Rigid-rod polymers are often Hquid crystalline polymers classified as lyotropic, such as the aramids Nomex and Kevlar, or thermotropic Hquid crystalline polymers, such as Vectran. 

PBO andPBZT. PBZ, a family of/ -phenylene-heterocycHc rigid-rod and extended chain polymers includes poly(/)-phenylene-2,6-benzobisthiazole) [69794-31-6] trans-V 27V) and poly(/)-phenylene-2,6-benzobisoxazole) [60871-72-9] (ot-PBO). PBZT and PBO were initially prepared at the Air Force Materials Laboratory at Wright-Patterson Air Force Base, Dayton, Ohio. PBZT was prepared by the reaction of... 

In the ordered smectic or nematic phase, the rigid rods are arranged in parallel arrays that allow for close packing. The nematic phase is the most common type found with synthetic polymer molecules. The molecules long axes are parallel, but there is no layering. Aromatic polymer chains that have stiff ester or amide linkages are ideal. 

Poly(p-pheny lene)s, PPPs, constitute the prototype of rigid-rod polymers and are currently being intensively investigated [1]. The key role of PPPs follows from their conceptually simple and appealing molecular structure, from their chemical stability, and from their superior physical properties [2], In turn, this is the result of important advances made in aromatic chemistry over the last few years. The following section gives an overview of the most common methods to generate poly(p-phenylene)s via different synthetic approaches. 

The main chain of dendronized polymers, due to die large size of the mon-odendrons, is usually forced to take a stretched shape thus the whole molecule exists as a rigid rod architecture both in solution and in the solid state.32d Depending on the backbone stiffness, the degree of monodendron coverage, and the size of die monodendron, the architecture of these macromolecules is no longer a sphere but a cylinder this dictates die properties of the dendronized polymers. 

The rheological behaviour of polymeric solutions is strongly influenced by the conformation of the polymer. In principle one has to deal with three different conformations, namely (1) random coil polymers (2) semi-flexible rod-like macromolecules and (2) rigid rods. It is easily understood that the hydrody-namically effective volume increases in the sequence mentioned, i.e. molecules with an equal degree of polymerisation exhibit drastically larger viscosities in a rod-like conformation than as statistical coil molecules. An experimental parameter, easily determined, for the conformation of a polymer is the exponent a of the Mark-Houwink relationship [25,26]. In the case of coiled polymers a is between 0.5 and 0.9,semi-flexible rods exhibit values between 1 and 1.3, whereas for an ideal rod the intrinsic viscosity is found to be proportional to M2. 

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